This application pertains to the art of medical diagnostic apparatus and more particularly to noninvasive measurement of cardiac functions. The invention is particularly amenable to combination with an esophageal stethoscope and will be described with particular reference to this combination. However, it will be appreciated that the invention has broader aspects. For example, the invention may be utilized independent of any audio esophageal stethoscope, or in combination with other monitoring apparatus. Further, the present invention may be disposed in other body passages for noninvasive measurement of cardiac or other physiological functions.
In the past, precordial stethoscopes, seismometers and accelerometers have all been used to monitor cardiac and other physiological functions from the exterior of the patient. Precordial and esophageal stethoscopes have been used for audibly monitoring patients' cardiac functions. However, cardiac motion produces energy and also provides information at frequencies below the threshold of human hearing. Moreover, simple precordial and esophageal stethoscopes produce no electrical signals. Accordingly, this acoustic information is not readily converted to a visual display, recorded, or processed to extract more sophisticated significance from the information. In the past, esophageal stethoscopes have been combined with electronic detectors such as thermistors for monitoring temperature or pressure transducers for monitoring esophageal motility. However, these electronic devices generally measure different and additional physiological parameters than the stethoscope.
One of the problems with the prior art of precordial and esophageal stethoscopes is that they are unsuited for monitoring data at frequencies below the audio frequency range. Another problem has been the inability to record or process the information monitored.
The prior art has lacked a noninvasive apparatus for internally measuring cardiovascular acceleration, velocity, or displacement produced by the cardiovascular system.
The present invention contemplates a new and improved noninvasive cardiovascular monitoring apparatus which overcomes the above-referenced problems and others. The present invention provides an accurate cardiac monitoring apparatus which is relatively easy to use, relatively inexpensive, and readily adaptable for use in conjunction with commonly used medical apparatus. In accordance with the present invention there is provided an esophageal cardiovascular monitoring apparatus. The apparatus includes an electrokinetic transducer for generating electrical signals which are indicative of its movement. The electrokinetic transducer is adapted to be disposed within the esophagus of the patient generally adjacent the patient's heart. The apparatus further includes an esophageal positioning means for selectively positioning the electrokinetic transducer in the patient's esophagus. Electrically connected with the electrokinetic transducer is a representation producing means for producing a representation which is indicative of a function of the movement of the electrokinetic transducer.
In accordance with a more limited aspect of the invention there is provided an esophageal stethoscope for audibly and electronically monitoring a function of the cardiovascular system of a patient. The stethoscope includes a flexible tube adapted to be disposed within the patient's esophagus. Disposed adjacent one end of the tube there is at least one aperture. A sound transmitting membrane is disposed adjacent the one end of the tube such that it covers the aperture for permitting sound to be received within the tube. An ear piece is acoustically connected with the tube to enable an operator to listen to sounds which are carried by the tube. An electrokinetic transducer is disposed adjacent the one end of the tube to produce electric signals indicative of a function of its movement. A signal processing means receives the electrical signals from the electrokinetic transducer and produces a representation which is indicative of a preselected function of the movement of the accelerometer. A display means is connected with the signal processing means to produce a visual display of the representation.
A principal advantage of the present invention is that it produces very accurate measurements of cardiac functions with a noninvasive apparatus. The apparatus has a very high signal to noise ratio.
Another advantage of the present invention is that it collects information which was heretofore not monitored. Yet another advantage of the present invention is that it stores and processes the monitored information.
Yet another advantage of the present invention is that it interfaces readily with currently available medical electronics.